A liquid crystal display device is configured by a liquid crystal layer, a backlight device, and the like. The backlight device in such a liquid crystal display device includes a device using white light, and a device that emits white light by mixing three primary colors (for example, red, green, and blue). In the backlight having three-color light sources, adjustment of white balance (chromaticity of a white point) is performed by changing the balance of brightness of the three colors (for example, refer to Patent Document 1).
In a display device that displays a graphic image for medical use or the like, it is desired to maintain a certain brightness desired by a user for a long time. In a display device in which a backlight used for such an application has a light source configured by three-color cold-cathode tubes, a gain with respect to a video signal to be input so that the white balance becomes a desired balance has been set at the time of shipment, and device chromaticity has been adjusted by the set gain. The device chromaticity is the chromaticity of a white point, at which the brightness becomes highest in an own display device, and is the chromaticity of the white point obtained at the time of providing maximum power to the backlight and maximum tone to the video signal. The white point is also referred to as a “Native white point” in manufactured products. In a display device that maintains a constant brightness, if the device chromaticity is degraded with time and a difference in chromaticity in a color space between the device chromaticity and the set chromaticity increases, degradation of brightness is likely to occur. The set chromaticity is the chromaticity of the white point based on user setting.
Therefore, in the display device that maintains a constant brightness, even if the display device changes over time, correction is performed by using a correction value with respect to the white balance at the time of shipment, to keep the difference in chromaticity between the device chromaticity and the set chromaticity constant, thereby reducing a decrease in brightness.